嵌入式中的C：结构体 位域操作

结构体后缀 :1

typedef union {
	struct {
		unsigned long	P0:1;
		unsigned long	P1:1;
		unsigned long	P2:1;
		unsigned long	P3:1;
		unsigned long	P4:1;
		unsigned long	P5:1;
		unsigned long	P6:1;
		unsigned long	P7:1;
		unsigned long	P8:1;
		unsigned long	P9:1;
		unsigned long	P10:1;
		unsigned long	P11:1;
		unsigned long	P12:1;
		unsigned long	P13:1;
		unsigned long	P14:1;
		unsigned long	P15:1;
		unsigned long	P16:1;
		unsigned long	P17:1;
		unsigned long	P18:1;
		unsigned long	P19:1;
		unsigned long	P20:1;
		unsigned long	P21:1;
		unsigned long	P22:1;
		unsigned long	P23:1;
		unsigned long	P24:1;
		unsigned long	P25:1;
		unsigned long	P26:1;
		unsigned long	P27:1;
		unsigned long	P28:1;
		unsigned long	P29:1;
		unsigned long	P30:1;
		unsigned long	P31:1;
	}BIT;
	
	unsigned long	WORD;
}Reg_GPIO_PORT;

定义一个联合体来描述32位寄存器。
对于其中的BIT结构体，可以看到P0:1这样一个操作。

这是位域操作的表示方法，也就是说后面加上“:1”的意思是这个成员的大小占所定义类型的1 bit，“：2”占2 bit，依次类推。当然大小不能超过所定义类型包含的总bit数。